It is fair, I think, to say that there wouldn’t be a “high end” as we now know it if it weren’t for the Audio Research Corporation, whose founder and chief designer, William Zane Johnson, virtually single-handedly rescued the “old-fashioned” tube from the junk pile of history when he introduced his “High Definition” line of glass-bottle electronics in 1970. Although the product under review commemorates the fortieth anniversary of this debut, Johnson had actually been working on tube circuits since getting out of the service in the late 1940s. In fact, in 1951 he started his first company—Electronic Industries—to build one-at-a-time amps for friends and customers (and to repair all manner of electrical gear). In 1968, Electronic Industries was purchased by a larger company called Peploe, Inc., which subsequently marketed Johnson’s first “widely” available tube amp. (The Dual 100—a two-chassis [separate power supply and amplifier connected via an umbilical], 6550-based, 100Wpc stereo unit—is reputedly a great-sounding amplifier, so good and seminal that Naoto Kurosawa, the brilliant designer behind Technical Brain electronics, gives a pristine sample of it pride of place in his showroom in Kawagoe, Japan.) In 1970, Johnson left Peploe, where he had been Technical Director, and went back into business for himself, founding the Audio Research Corporation.

Old-fashioned tube designs were in steep decline by then, new-fangled transistors in full ascendance. In fact, when Johnson showed his first ARC tube products—the Dual 50 power amplifier and the SP-1 and SP-2 preamps—at a trade show in Washington, D.C. in 1970 (as Robert Harley relates in an interview he conducted with WZJ for Stereophile back in 1994), a furious audio engineer walked up to him and shouted, “You’ve set the industry back 20 years!”

That angry audio engineer clearly wasn’t listening closely (a turn-of-events that has never since been repeated, I’m told), because from go William Zane Johnson’s tube designs never sounded anything like the vintage gear of companies such as Marantz and McIntosh. His amps and preamps weren’t murky; they weren’t ill-defined; they weren’t sloppy in the bass and rolled-off in the treble. Neither did they sound “voluptuous,” or “liquid,” or chocolaty “dark and sweet.” (Maybe that angry audio engineer was listening, after all.) From the start, Johnson made it his goal to add the speed, resolution, and neutrality of solid-state to the bloom, air, and incomparable timbral and textural magic of tubes, aiming at a kind of unified field theory of glass-bottle electronics.

There’s no need (nor space) to review all the high points in ARC’s illustrious forty-year history. From the D-150 amp and SP-3 preamps, which thanks primarily to Harry Pearson and TAS, really put Audio Research on the map, through the D79 amps and SP-10 preamps to the current highly regarded Reference Series products, Johnson and his ARC team have steadily come closer and closer to achieving their goal of importing the virtues of solid-state into a tube circuit, without sacrificing the virtues of tubes. And now, with the Fortieth Anniversary Edition Reference preamp, they’ve not only reached their objective; they’ve exceeded it, which, I suppose, is only befitting for a product with such an ambitious moniker.

A two-box preamp (separate power supply and linestage connected by two supplied umbilicals)—the first two-box tube preamp from ARC I’ve had in my system since the fabled SP-10 Mk II—the Fortieth Anniversary Edition Reference (hereafter, the Ref 40) not only matches (or very, very nearly) the frequency extension, resolution, grip, and transient speed of almost every solid-state linestage I’ve heard (there is an exception I will come to); it also adds a dose of pure tube magic the likes of which both Robert Harley and I have never heard before—from ARC or anyone else. It is almost an irony that in advancing ever more closely toward a “unified” tube-hybrid sound, ARC has rather left advances in “classic” tube sound behind. Here, it more than makes up for lost ground, taking one of the chief virtues that tubes are justly famous for to an unparalleled level of realism.

Before I get to these sonic wonders, let’s look at what ARC hath wrought inside the Ref 40’s two chassis. (I’m reminded of the scene in Monkey Business, where, as Chico launches into the obligatory novelty piano number, Groucho turns to the camera and says to the audience: “I gotta stay here, but why don’t you folks go out to the lobby and catch a smoke?” If you feel that way about reviewers parroting Web site specs and designer propaganda ad nauseum, why don’t you go catch a smoke and return in a paragraph or three?)

The first things you will notice when you pop the lid on the preamp section of the Ref 40 to install the tubes are (as ARC correctly notes) the four humongous proprietary Teflon coupling caps on the left side of the chassis (the Teflon bypass caps are mounted on the bottom of the main board, out of sight). Each of these coupling caps weighs more than two pounds! Which (in concert with the added capacitance in the beefed-up dual-mono power supply) is a large part of the reason why the Anniversary Edition preamp has so much more speed and clout than any previous ARC linestage (and a large part of the reason why this preamp takes so very long—at least 400 to 500 hours—to break in).

The audio circuit board itself looks a little like a Reference 5 that’s been exposed to radiation from the same plutonium bomb that caused Col. Glen Manning to grow into The Amazing Colossal Man. Everthing’s bigger and more plentiful, not just the gigantic coupling caps. The dual-mono, zero-feedback, Class A analog gain stages use four 6H30 triodes per channel (the Ref 5 uses two). The separate dual-mono power-supply chassis also has twice the number of tubes—separate pairs of 6550C and 6H30s to regulate each channel—twice the number of transformers—one low-voltage and one high-voltage for each channel—and twice the capacitance of the Reference 5.

Among the many other salient things that all this excess buys you is much lower distortion. Where the Ref 5 spec’d out at less than 0.01% THD at 2V out, ARC claims the Ref 40 has 0.006% THD at 2V out, which approaches Soulution territory—a first, in my experience, for a tube preamplifier. I’ve no way to verify these numbers, save by ear, but ears will do in this case because it will be immediately obvious to any listener that the Ref 40 is not only immensely faster and more powerful than the Ref 5; it is also much lower in tube-like noise and coloration—and hence much more delicate in texture, neutral in balance, and higher in low-level resolution.

As long as we’re engaging in invidious comparisons, some of you may have wondered why my TAS review of the ARC Reference 5 preamp (in Issue 205) was relatively succinct. Well, there were two reasons actually. First, I knew that the Anniversary Edition Reference preamp was waiting in the wings, and since I expected it to be special, I wanted to leave room for it, critically speaking. Second—and more importantly—as good as I think the Reference 5 is (and it is—or was—my reference preamp), I didn’t think it was as big an advance over ARC’s Reference 3 preamp as, say, the Reference 3 was over the Reference 2. Although better in every way than the Reference 3, the Ref 5 was not fundamentally different-sounding than the Ref 3; it was more like a “hot-rodded” version of it.

The Anniversary Edition Reference preamp is fundamentally different-sounding—not just than the Reference 3 or 5 but than any preamp, tube or solid-state, I’ve heard. The Anniversary Edition Preamp is also more realistic than any preamp I’ve yet heard (save for two others that I will come to anon). Of course, at $25,000 the ARC Anniversary Edition Reference ought to be better than ARC’s previous efforts, but this much better? Frankly, I didn’t expect it. I doubt if anybody could have; differences this big and basic don’t come along everyday.

It’s pretty easy to describe what the Ref 40 does that sets it off from the long long line of its distinguished forbears, and you won’t need “golden ears” to hear it for yourself.

Quite simply, this is the most holographic preamp I have (and, I am willing to bet, you have) ever listened to. Although ARC has long held a patent on dimensionality and bloom—and dimensionality was one of the two areas in which the Reference 5 was markedly improved over the Reference 3—folks, you ain’t heard nothing yet!

What the Ref 40 does that no other preamp I’ve heard does is reproduce instruments and vocalists with a three-dimensional “solidity” (the very meaning of the word “stereo,” BTW) that is simply mind-boggling (and unequaled in my experience). Instruments are so rooted in space, so solidly “there,” and the stage is so clear and orderly, it is almost like you’re listening to a three-channel system playing back three-channel mastertapes—that “phantom” center channel is that much less phantom. Trust me: The difference is that dramatic.

A plethora of improvements have gone into making these far more solid and lifelike images. First there is a sheer density of tone color such as I’ve never before heard from any ARC preamp, which, in the past, have tended toward a lighter, brighter presentation of timbre, usually caused by a slight characteristic recessiveness in the upper bass and lower midrange and a slight characteristic rise in the upper mids (though both recessiveness and rise have been reduced to minims in recent ARC units). Not the Ref 40, whose weight and fullness of tone color bespeak unusually realistic upper bass, lower midrange, and treble response and are a large part of what makes those instrumental and vocal images so shockingly solid and holographic.

Usually, you have to give up some transient speed and transparency to achieve this kind of density of timbre. Not with the Ref 40. In fact, I’ve never heard a tube preamp and only two or three solid-state preamps that have the transient speed of this one. Plucked sting instruments, such as the kotos and violins in Christopher Campbell’s Sound the All-Clear [Innova], have the electrifying string-against-wood report of the real thing in a real space. Ditto for sharply struck drums and cymbals on the same disc. What’s amazing is that these instruments don't just have lifelike attack; they also have the body and sustain of the real things. The Ref 40 does not trade off timbre and duration for speed, or vice versa.

And then there is the Ref 40’s dynamic range. It is literally shocking (and goosebump-inducing) to hear how realistically this preamp reproduces powerful instruments, like the big brass choir on the right hand side of the stage in the third movement of Janacek’s Sinfonietta [Denon]. Outside of a concert hall, I don’t think I’ve heard a mere stereo system reproduce brass with such lifelike authority and presence. Ditto for solo piano. On good recordings—such as Orion LP of Ingolf Dahl’s lyrical sonatas—the Ref 40 makes a concert grand more "there" than any other preamp I’ve had in my system. As with timbre, there is a solidity to the Ref 40’s presentation of dynamics—a continuousness, if you will—that makes other preamps sound like they’re peaking or losing steam or breaking up at various points along the dynamic continuum.

Don’t even ask about soundstaging. When individual instruments are this “rooted” in place—this solid and realistic in color and dynamic—it becomes a lot easier to visualize them on stage, even when they are parts of large choirs.

As for retrieval of low-level detail, the Ref 40 is, as noted, vastly superior to the Reference 5, which was the most detailed ARC preamp I’d heard. Whether it equals that champeen of low-level resolution, the Technical Brain TBC Zero, remains to be seen or heard. (I’ll get the TBC back after the Rocky Mountain Audio Fest and let you know.) At this point, I’d have to say that the Ref 40 certainly doesn’t seem to be missing much—if anything—in comparison to another paragon of low-level resolution, the Soulution 720 preamplifier.

For instance, when I went to Berkeley last month to visit Magico, I was amazed by the resolution of the Q5s driven by Soulution electronics. One cut in particular floored me. Toward the start of the cut “Sound the All-Clear,” a woman starts counting softly amid a racket-like fortissimo of percussive instruments: "One, two, three, four, FIVE." In my home system, through the Reference 5 and several speakers I was then testing, all I could clearly hear without straining was "Five." In Berkeley, through the Q5s and the Soulution 720/700s, every single number that the woman uttered was as clear as day, no matter how loudly the surrounding instruments were playing.

I thought this was a testament to the fantastic resolution of the Q5s (and the Soulution gear), which, indeed, it was. But when I got home, I swapped out the speakers under test for the TAD CR-1 compact monitors and the Reference 5 for the Reference 40 and, sure enough, heard the same thing that I’d heard in Berkeley (albeit without the Q5s’ fabulous bottom octave—and a few other things that speaker did incomparably well).

Of course, this was a comparison to Soulution electronics, and I know that the Technical Brain TBC Zero has even higher resolution than the Soulution 720 (though, perhaps, not as much timbral “meat” on its bones or as much heft in the bass). So, as I said, we’ll wait and see how the Ref 40 fares against it. Frankly, until the Ref 40, I’d never auditioned another preamp that could reproduce whole sets of data I hadn’t heard before from familiar discs with the regularity of the Technical Brain TBC Zero. But when it comes to holographic imaging and realistic timbre and dynamic authority and lifelike solidity, the Ref 40 clearly does the same thing. It may, indeed, be doing the same thing with low-level detail. If it isn’t, there is only one other that I’ve heard that may better it. We’ll see.

It is genuinely thrilling to listen to a piece of gear that makes instruments and vocalists on familiar records sound consistently and unmistakably more like real instruments and real singers. In fact, I didn't think there is a bigger thrill in audio. The Reference 40 supplies that thrill on every LP or CD you listen to. It is, in my opinion, the single best product ARC has made in its 40 years of excellence—an instant audio classic. Naturally, it gets my highest recommendation. In our current issue, it also wins TAS’s highest award, Overall Product of the Year. ’Nuff said.

Design, Setup, and Operation

Though the Reference 40 builds upon the work of ARC’s founder William Zane Johnson—and is a paean to his life’s work—it is not strictly speaking a Johnson design. It is primarily the work of ARC’s Managing Director of Engineering, Ward Fiebiger, with the voicing done by ARC’s Head of Sonic Development, Warren Gehl.

It may be a little early to say this, but I’ve got the feeling that the Ref 40 is not just a culmination; it is a new beginning for Audio Research. The difference in the preamp’s overall character—the uncharacteristic richness of its timbre, its newfound low-level resolution and vanishingly low tube noise, its tremendous dynamic range and scale, its greatly improved grip, clarity, and definition in the bass (which now challenges, if not quite equals the very best solid-state), and, of course, its magical three-dimensionality and solidity are, to varying degrees departures from or improvements on the present-day ARC “norm.” Those who have been bothered by the leaner, brighter sound of previous “high-definition” ARC preamps (or its lack of grip in the bass) should most definitely give this one a listen. I look at the Ref 40 not just as a triumph of engineering but as a herald of great things to come (particularly in amplification), and I sincerely hope that it is not, as originally planned, limited to a one-year run (ending in April of 2011). It would be tragic if a product this wonderful weren’t widely available for more than such a relatively short time. Certainly, its cost will limit its sales (in spite of its superiority to the Reference 5, that less-expensive preamp remains the next-best choice for those ARC fans who can’t afford the Ref 40), but even at $25k the Ref 40 is a relative bargain (as ARC components have always been) considering the competitors it is playing against.

As for setup, after tube installation certain precautions have to be taken with the two-chassis Ref 40. Most critically, its power cord must be unplugged when you attach or detach the two umbilical cords that go from the power supply to the linestage. In addition, the number of tubes in each chassis generate a good deal of heat, making “stacking” the units impractical. Although I suppose it could be done if you left sufficient space between the two chassis for both units to “breathe,” stacking is not recommended by ARC, and the umbilicals have been made long enough to facilitate placement on widely-spaced separate shelves.

I suppose I should note that Robert Harley, who got a Ref 40 before me, had a problem with his unit, which turned out to be a combination of faulty tubes and poor planning on ARC’s part (the unit he was originally provided was the one ARC had sent to a safety lab for testing, which included baking it in a high-temperature oven—not a good idea for a review sample). I also had an as-yet-undiagnosed problem with one channel of the power supply in my unit—the first time I’ve ever had a problem (other than a worn-out tube) with an ARC preamp. I believe I was just unlucky, because ARC reports no other such problems with Ref 40s in the field. Plus, given the sound of a fully broken-in Ref 40, who cares?

Speaking of break-in, one thing that all Ref 40 owners should be aware is that this will take an unusually long time. Chiefly because of those four two-pound-apiece capacitors, the Ref 40 makes the sluggish Ref 5 looks like a morning glory when it comes to opening up and showing its best. Indeed, I’m told that the Ref 40 keeps improving in sound up to 1000 hours (which is nearly a quarter the life of the tubes). I can tell you from my own experience that its sound does keep getting better with play, and that you will have to burn it in for at least 400 hours before you start to hear much of what it is capable of. Once broken in, it also sounds better after its been on awhile (at least a half an hour in my experience), which is typical of both tube and solid-state preamps.

Like all contemporary ARC units, the Ref 40 comes with a dinky but useful remote control that duplicates all the controls on the audio chassis, making it a snap to change or mute volume, switch inputs, adjust channel balance, toggle to mono, among other niceties. Again like all contemporary ARC units, the Ref 40 has a fluorescent front-panel display which, for best sonics, is better left dimmed (another adjustment you can effect via the remote). Even when dimmed, the display will light up briefly when you make a change and its alphanumeric readout is large enough to be easily read from across a room.

Though the Ref 40 (like other ARC products) comes with a good IEC power cord, it sounds better (like other ARC products) with a first-rate aftermarket cord. I can recommend those from Synergistic Research, Shunyata, and Tara Labs, although I’m sure any top-line cord will do.

As for balanced versus single-ended performance, in the past I’ve preferred the sound of ARC run single-ended (although there are some trade-offs in noise and output). I’m not at all sure, however, that that longstanding preference holds with the Ref 40, which seems to sound best (and is designed to sound best) when run balanced. I can certainly say that I prefer using balanced wire, where feasible, between the preamp and the amp (I’ve tried and been delighted with top-line balanced interconnects from Synergistic Research, MIT, and Tara Labs, but once again I’m sure that any very high-quality wire would suffice.) JV